Toyota Nation Forum banner

05 Camry P304 Misfire

1341 Views 2 Replies 2 Participants Last post by  Propane Camry
05 Camry 2.4L. ~ 250K hassle free miles. Runs on both propane and gasoline.

Issue: p304 #4 misfire.

1- Checked plugs. Everything seemed ok. Replaced and properly gaped plugs. No change.

2- Checked for vacuum leaks. Sprayed all vac lines with starting fluid. No leaks detected.

3- Ruled out bad fuel injector by running the car on propane. The propane system uses a separate fuel injector system for injecting the propane into the intake runners. The propane computer piggybacks on the OEM sensors and will cut out the signal to the gasoline injectors and instead fire the propane injectors.

4- Swapped coils. Still # 4 misfire. Later replaced #4 coil. No resolution.

5- Downloaded Torque app and started monitoring engine sensors. Noticed that during acceleration the MAF would periodically lose signal. First cleaned MAF using the MAF cleaner and later replaced the MAF. No changes. See screenshot below.

6- Continued to monitor the sensors and noticed that the MAF signal and vacuum signal would drop off. I later concluded that this appears to start happening ~ 2500 RPM. After some research, I noticed that the vacuum switching valve kicks in at 2500 RPM. I thought I had my answer. I replaced the switching valve (the one mounted on the air intake hose) with one at the salvage yard and I still have the same issue.

7- The manual i purchased does not have engine wiring diagram. It only has the stuff for power locks, windows, radio, etc. No sensor wiring diagrams. I need a detailed wiring diagram.

What are my other options? Need advise.

I have not checked the compression. I ruled this out when I noticed the sensor signal issues. I have always monitored the oil via oil analysis and never noticed any excessive wear metals in the oil.

I suspect there is a wiring issue on a wire that is running the vacuum switching valve or the MAP. Other potential issue is faulty computer.
See less See more
1 - 3 of 3 Posts
Go to may have diagram you need.
I wanted to give an update. I did a compression check and I had low compression in the #4 cylinder. I purchased a parts car and swapped engines. When removing the engine, I could see valve damage on the #4 through the exhaust port. I have not removed the head yet for closer inspection so I am not 100% sure what caused the issue yet.
  • Like
Reactions: 1
1 - 3 of 3 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.